Note: Descriptions are shown in the official language in which they were submitted.
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COMPACT ANTENNA PHASE SHIFTER WITH SIMPLIFIED DRIVE
MECHANISM
CROSS REFERENCE TO RELATED DISCLOSURE
[00011 This
application is based upon and claims priority to, under relevant sections
of 35 U.S.C. 119, U.S. Provisional Patent Application No. 62/661,230, COMPACT
ANTENNA PHASE SHIFTER WITH SIMPLIFIED DRIVE MECHANISM filed April 23,
2018, the entire contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
Field of the invention
[00021 The
present invention relates to wireless communications, and more
particularly, to small cell antennas incorporating mechanical phase shifters.
Related Art
[00031 Urban
deployments of cellular network require antennas that are compact and
offer a variety of gain profile configurations. A solution to this challenge
is a cylindrical
antenna having several internal array faces, or sectors, each corresponding to
a given
azimuthal portion of a 360 degree area of angular coverage. Often, depending
upon the
coverage area desired, it may be necessary for an antenna to have the ability
to tilt its gain
downwardly or upwardly. Such gain pattern adjustment is conventionally
achieved with
phase shifters that may be integrated into each antenna array face.
[00041
Conventional phase shifters have wiper arms that are individually engaged at
the wiper arm distal end (opposite from the pivot end). This configuration has
two principal
disadvantages: (1) it increases the materials and number of parts associated
with the phase
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shifter; and (2) it restricts the ability to reduce the size of the array
face. The latter
complication arises inasmuch as the wiper arms require a drive mechanism that
extends to
the outer edges of the array face along the azimuth axis. In the case of a
small cell antenna,
having a cylindrical configuration with three array faces, or sectors, (each
oriented at 120
degree intervals, for example), a conventional drive mechanism interferes with
the other
array face PCBs. This is due to the configuration of the drive mechanism which
is disposed
at the outer edges of its respective array face. As such, the drive mechanism
interferes with
the other PCBs, i.e., where they meet.
[00051
Accordingly, a need exists for a phase shifter having a minimal profile and
part count, enabling mounting of multiple array faces within a
cylindrical/sector antenna.
SUMMARY OF THE INVENTION
[00061 An
aspect of the present invention involves a phase shifter arrangement for an
antenna. The phase shifter arrangement has pair of phase shifters, each phase
shifter having a
first wiper arm and a second wiper arm, the first and second wiper arm each
having a
proximal end and a distal end and a pivot axis disposed between the proximal
end and the
distal end. The first and second wiper arm each have a wiper arm conductive
trace disposed
on its underside wherein the conductive trace is disposed between the pivot
axis and the
distal end, and a drive pin slot disposed between the pivot axis and the
proximal end. The
phase shifter arrangement has a drive shaft that has a longitudinal axis and
two drive pins,
wherein the drive pins are disposed on opposite sides of the drive shaft at a
lateral distance
from the longitudinal axis of the drive shaft and mechanically coupled to the
drive shaft by a
plurality of struts. Each of the drive pins mechanically couples to a
corresponding first wiper
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arm and second wiper arm of each of the pair of phase shifters, wherein as the
drive shaft
translates along the longitudinal axis, each drive pin slides within the drive
pin slots of the
corresponding first wiper arm and second wiper arm, causing the first wiper
arm and second
wiper arm to rotate in unison about their corresponding pivot axes.
[00071 Another
aspect of the present invention involves an antenna that comprises an
RF signal input port, a plurality of radiators, and a phase shifter
arrangement electrically
coupled between the RF signal input port and the plurality of radiators. The
phase shifter
arrangement has a pair of phase shifters, each phase shifter having a first
wiper arm and a
second wiper arm. The first and second wiper arm each have a proximal end and
a distal end
and a pivot axis disposed between the proximal end and the distal end. The
first and second
wiper arm each have a wiper arm conductive trace disposed on an its underside
wherein the
conductive trace is disposed between the pivot axis and the distal end, and a
drive pin slot
disposed between the pivot axis and the proximal end. The phase shifter
arrangement has a
drive shaft having a longitudinal axis and two drive pins, wherein the drive
pins are disposed
on opposite sides of the drive shaft at a lateral distance from the
longitudinal axis of the drive
shaft and mechanically coupled to the drive shaft by a plurality of struts,
wherein each of the
drive pins mechanically couples to a corresponding first wiper arm and second
wiper arm of
each of the pair of phase shifters. As the drive shaft translates along the
longitudinal axis,
each drive pin slides within the drive pin slots of the corresponding first
wiper arm and
second wiper arm, causing the first wiper arm and second wiper arm to rotate
in unison about
their corresponding pivot axes.
[00081 Another
aspect of the invention involves an antenna having a plurality of array
faces, each of the plurality of array faces corresponding to a distinct
azimuth angle of
coverage. Each of the array faces comprises a PCB structure, a plurality of
radiators disposed
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on the PCB structure, and a phase shifter arrangement disposed on the PCB
structure. The
phase shifter arrangement has a pair of phase shifters, each of the phase
shifters electrically
coupled between one or more RF signal inputs and the plurality of radiators.
Each phase
shifter has a first wiper arm and a second wiper arm, the first and second
wiper arm each
having a proximal end and a distal end and a pivot axis disposed between the
proximal end
and the distal end. The first and second wiper arm each have a wiper arm
conductive trace
disposed on an its underside wherein the conductive trace is disposed between
the pivot axis
and the distal end, and a drive pin slot disposed between the pivot axis and
the proximal end.
The phase shifter arrangement has a drive shaft having a longitudinal axis and
two drive pins,
wherein the drive pins are disposed on opposite sides of the drive shaft at a
lateral distance
from the longitudinal axis of the drive shaft and mechanically coupled to the
drive shaft by a
plurality of struts, wherein each of the drive pins mechanically couples to a
corresponding
first wiper arm and second wiper arm of each of the pair of phase shifters. As
the drive shaft
translates along the longitudinal axis, each drive pin slides within the drive
pin slots of the
corresponding first wiper arm and second wiper arm, causing the first wiper
arm and second
wiper arm to rotate in unison about their corresponding pivot axes.
BRIEF DESCRIPTION OF THE DRAWINGS
[00091 So that
the manner in which the features of the invention can be understood, a
detailed description of the invention may be had by reference to certain
embodiments, some
of which are illustrated in the accompanying drawings. It is to be noted,
however, that the
drawings illustrate only certain embodiments of this invention and are
therefore not to be
considered limiting of its scope, for the scope of the disclosed subject
matter encompasses
other embodiments as well. The drawings are not necessarily to scale, emphasis
generally
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being placed upon illustrating the features of certain embodiments of the
invention. In the
drawings, like numerals are used to indicate like parts throughout the various
views.
[00101 FIG. 1
illustrates an exemplary cylindrical/sector antenna according to the
disclosure wherein tri-sector antennas, each spanning one-hundred and twenty
degrees of
coverage.
[00111 FIG. 2
illustrates an exemplary phase shifter assembly according to the
disclosure, as seen from the outward-facing side of an antenna array face.
[00121 FIG. 3
illustrates an exemplary phase shifter assembly according to the
disclosure, as seen from the inward-facing side of an antenna array face.
[00131 FIG. 4
illustrates an exemplary phase shifter wiper arm according to the
disclosure.
[00141 FIG. 5
is an edge view of an array face Printed Circuit Board (PCB) with a
single phase shifter pair according to the disclosure.
[00151 FIG. 6a
illustrates an internal perspective view of a sector antenna and an
independently-driven phase shifter assembly for a single sector thereof.
[00161 FIG. 6b
illustrates an internal perspective view of an omni-directional sector
antenna and a commonly-driven phase shifter assembly for driving all sectors
of the omni-
directional antenna.
[00171 FIG. 7a
is a top view of the sector antenna shown in Fig. 6a depicting tri-
sector arrays and an independently-driven phase shifter assembly disposed
along the internal
face of each sector.
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[00181 Fig. 7b
is a top view of the omni-directional sector shown in Fig. 7b depicting
a vertical shaft/spoked-web for simultaneously driving the phase shifters
along all sectors of
the omni-directional antenna.
DETAILED DESCRIPTION
[00191 The
invention is directed to a phase shifter assembly wherein each wiper arm
has a pivot point disposed proximal the center of a wiper arm, and wherein the
end opposite
the distal end engages with a drive pin. Both wiper arms of the phase shifter
engage with a
single drive pin and thus are both driven by a single shaft that is coupled to
a drive motor.
[00201 The
phase shifter assembly according to the disclosure requires less material
and fewer parts than a conventional phase shifter. Further, because the drive
mechanism is
located substantially at the center of the phase shifter (along the azimuth
axis), there is more
room at the outer edges of the array face PCB to enable the shrinking of the
array face in the
azimuth dimension, enabling a smaller small cell antenna.
[00211 FIG. 1
illustrates an exemplary small cell antenna 100. Antenna 100 may have
a plurality of array faces 110a, 110b, and 110c, each of which corresponding
to an azimuth
direction A, B, and C, whereby each array face 110a, 110b, 110c has a gain
pattern that
substantially covers its corresponding azimuthal portion of 360 degrees.
Azimuth directions
A, B, and C may each be orthogonal to the surface of their corresponding array
faces 110a,
110b, 110c, and each may be orthogonal to the tilt (or vertical) axis z. The
exemplary
antenna 100 has three array faces, each spaced at 120 degrees, however, it
will be understood
that variations to this design, including the number and angular orientations
of the array
faces, are possible and within the scope of the disclosure. For example, each
array face may
span ninety (90) degrees or sixty (60) degrees.
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[00221 Each of
the array faces 110a, 110b, 110c has a printed circuit board (PCB)
structure 112, a plurality of radiators 130, and a phase shifter assembly 120.
Each phase
shifter assembly 120 provides a differential phase delay to sets of radiators
130 as a function
of their location along the tilt axis z. Generally, the radiators 130 located
at the center of the
array face 110a/b/c along the tilt axis (phase center) are not given any phase
delay, and rows
of radiators 130 are given an increasing differential phase delay as a
function of distance
from phase center along the tilt axis. The general principles of phase
shifters and how they
function are generally known in the art.
[00231 Among
the possible variations to the antenna 100 of the disclosure are two
configurations: tri-sector, and omni-directional. For the tri-sector
variation, each array face
110a, 110b, 110c operates independently. In the context used herein, the
independent
operation means that each array face 110a, 110b, 110c has its own RF signals
coupled to its
corresponding radiators 130, and each phase shifter 120 operates
independently. As such,
each 120 degree sector operates independently, i.e., is not influenced by the
RF signals in the
adjacent sectors. In an omni variation, the three array faces 110a, 110b, 110c
are unified in
that all of the radiators 130 on array faces 110a, 110b, 110c are coupled to
the same RF
signal sources, and the phase shifters 130 operate in unison.
[00241 FIG. 2
illustrates an exemplary phase shifter assembly 120 according to the
disclosure, as seen from the outward-facing side of an antenna array face 110
(use of "array
face 110" may simply be any or all of the array faces 110a, 110b, 110c). The
phase shifter
assembly 120 may include two pairs of wiper arms 205a and 205b, each of which
is
configured to rotate around their respective axis 210, and are mutually,
rotatably, and
mechanically coupled by a drive pin 215, which translates within a PCB slot
220. As
illustrated, the wiper arms 205a, 205b are oriented such that drive pin 215 is
located at or
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near the full extent of its motion within PCB slot 220. Further illustrated
(in dotted lines) are
wiper arms 205a, 205b with drive pin 215 in its center position within PCB
slot 220. Phase
shifter assembly 120 further includes PCB openings 225 and 230. PCB openings
225 and 230
which define an arcuate boundary corresponding to the sweep of the wiper arms
205a, 205b
as they rotate in response to translation of the drive pin 215 within the PCB
slots 220. Each
wiper arm 205a, 205b has a distal hook portion that mechanically engages with
the edge of
one of PCB openings 225, 230 (described below).
[00251 The
phase shifter assembly 120 includes a plurality of a first input/output RF
signal trace 24, each of which electrically couple one conductive trace to
another conductive
trace. For example, the wiper arm 205a, 205b may electrically couple a first
input/output RF
signal trace 24 to an second input/output RF signal trace 245.
[00261 By
placing the axis 210 proximal to the center of each of the wiper arms 205a,
205b, and by causing the wiper arms 205a, 205b to engage the drive pin 215 as
illustrated, it
is possible to drive both wiper arms 205a, 205b with a single drive mechanism
(described
below). In contrast, conventional wiper arms 205a, 205b have their axes at a
proximal end,
and are driven at their distal end.
[00271 FIG. 3
illustrates an exemplary phase shifter assembly 120 according to the
disclosure, as seen from an inwardly-facing side of an antenna array face 110.
Wiper
arms 205a, 205b are illustrated with dotted lines inasmuch as they are
disposed on the other
side of the PCB. Illustrated is a wiper arm drive shaft 300 that is
mechanically coupled to
drive pins 215 by support struts 305. Translation along the tilt (or
longitudinal) axis, causes
the drive shaft 300 to uniformly engage the drive pins 215 in parallel.
Accordingly, the drive
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shaft 300 drives the wiper arms 205a, 205b in unison within the respective PCB
slots 220.
As a consequence, the wiper arms 205a, 205b rotate about the respective pivot
points 210.
[00281 Fig. 4
depicts is an isolated perspective view of an exemplary wiper arm 205a
or 205b according to the disclosure. More specifically, and referring to FIGS
3 and 4, each of
wiper arm arms 205a, 205b has: (i) an aperture 405 for rotating about the
pivot axis 210, (ii)
a hook or recurved end portion 415 disposed at one end, and (iii) a slot 410
for accepting the
drive pin 215 which engages the wiper arms 205a, 205b as the drive shaft 300
translates with
the PCB slot 220. As mentioned hereinabove, the hook or recurved end portion
415 engages
an edge of the PCB opening 225, 230 to assure electrical coupling between the
wiper
arms 205a, 205b and: (i) a conductive trace, (ii) a first input/output RF
signal trace 240,
and/or (iii) a second input/output RF signal input trace 245. Each of the
wiper arms
205a, 205b also have a step feature 420, the height of which may vary from one
of the wiper
arms 205a, 205b to the other of the wiper arms 205a, 205b. Such features will
become
apparent in view of the following detailed discussion in FIG. 5.
[00291 FIG. 5
is an edge view of an antenna array face and printed circuit board
PCB 112 with a wiper arm pair 205a, 205b according to the disclosure. The
illustrated wiper
arm pair 205a, 205b may be either one of the two pairs within wiper arm
assembly 120.
Illustrated therein are PCB openings 225, 230, shown as gaps in the PCB 112;
wiper arms
205a, 205b (i.e., rotatably coupled to the PCB 112 via axis 210) and
translatably coupled to
the PCB 112 at an edge of the PCB openings 225, 230 via a distal hook 415. The
drive
pin 215 is coupled to both wiper arms 205a, 205b and is translatably disposed
within the
PCB slot 220.
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[00301 It will
be apparent that the first wiper arm 205a and the second wiper arm
205b define variable height dimensions with respect to each of their
respective step
features 420. Firstly, it will be apparent that for both wiper arms 205a, 205b
to engage the
drive pin 215, they must necessarily be staggered such that one is
superimposed over the
other. Secondly, even though the second wiper arm 205b is the "lower" of the
two wiper
arms 205a, 205b that its portion with drive pin slot 410 is closer to PCB 112
that is the
respective portion of wiper arm 205a, it continues to, or still, has a step
feature. This is due to
the fact that it remains desirable to provide distance between the lower of
the two wiper arms
205a, 205b with any of the input/output RF signal traces 515 so as to prevent
electrical signal
interference with the input/output RF signal traces 515.
[00311 Further
illustrated in FIG. 5 are wiper arm conductive traces 505 disposed on
the underside of wiper arms 205a, 205b. Wiper arm conductive traces 505
electrically couple
with RF signal traces 240, and imparts a phase delay on the RF signal traces,
depending on
the location of the RF signal trace (distal vs. proximal) and the angular
orientation of the
wiper arm 205a/b around the axis defined by pivot axis 210.
[00321 In FIGs.
6a and 7a, an internal perspective view of a sector antenna 110a is
depicted. More specifically, an independently-driven phase shifter assembly
120 is provided
for a single sector antenna 110a. Therein, a wiper arm (obscured by the PCB
structure) is
displaced and slid along the input/output RF traces by the input drive shaft
300. That is, the
wiper arms 205a, 205b are pivotally coupled to the input drive shaft 300 by
the drive pins
215 disposed at the distal ends of a support strut 305. A rotary actuator 610
turns a sector
drive shaft 605 which employs a worm gear transmission to covert the
rotational motion of
the actuator 610 into linear motion along the input drive shaft 300.
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[00331
Translation along the tilt (or longitudinal) axis, causes the drive shaft 300
to
uniformly engage the drive pins 215 in parallel and the wiper arms 205a, 205b
to rotate about
the respective pivot points 210. The top view of the sector antenna shown in
Fig. 7a depicts
at least three independently-driven phase shifter assemblies 120, each phase
shifter assembly
being disposed along the internal face of each sector.
[00341 In Figs.
6b and 7b, an internal perspective view of an omni-directional
antenna is depicted. More specifically, a plurality of commonly-driven phase
shifter
assemblies 120a, 120b, 120c are driven in unison by a drive shaft/strut
arrangement. Each of
the phase shifter assemblies 120a, 120b, 120c is displaced by a combination of
a central
shaft 650 and a spoked support strut 655, 660. The central shaft 610 is
slideably mounted to
the back-side of the PCB by a shaft fitting 665 and translates up and down by
a rotary
actuator 670.
[00351 More
specifically, a rotary actuator 670 drives a worm gear transmission to
covert the rotational motion of the actuator 670 into linear motion along the
central input
shaft 610. Translation along the tilt (or longitudinal) axis, is effected by
the drive shaft 650
which engages and pivots each of the wiper arms 205a, 205b about each of their
respective
pivot axes 210. The top view of the omni-directional antenna shown in Fig. 7a
depicts a
plurality of independently-driven phase shifter assemblies 120a, 120b, 120c
being displaced
by a commonly actuated central shaft 650.
[00361 While
the instant invention has been shown and described herein in what are
conceived to be the most practical and preferred embodiments, it is recognized
that
departures, modifications, adaptations, variations, and alterations in the
described methods
and systems may be made and will be apparent to those skilled in the art of
the foregoing
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description which does not depart from the spirit and scope of the invention
which is
therefore not to be limited to the details herein. For this reason, such
changes are desired to
be included within the scoped of the appended claims. The descriptive manner
which is
employed for setting forth the embodiments should be interpreted as
illustrative but not
limitative of the full scope of the claims which embrace any and all
equivalents thereto.
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